Ion beam etching is a method often utilized to prepare samples whose structure is then typically investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). This technology is used in particular in research, materials research, and quality control for many materials, such as semiconductors, metals, ceramics, plastics, and the like. To carry out the process, the samples are mounted on a sample stage of an ion beam etching unit, and aligned in the beam path of one or more ion beams. Ion beam etching units are typically high-vacuum units that work with a baseline pressure of 10−6 mbar. The ions most commonly used are argon ions, usually at an acceleration voltage from 1 to 10 kV. The quality of the image resolution in the electron microscope is very substantially dependent, in this context, on the quality of the prepared sample. Among the ion beam etching processes known in practice are, in particular, ion beam slope etching, ion polishing of SEM samples, the wire shadowing method, and ion beam preparation of standard TEM samples. While the last two methods are used for TEM samples, ion beam slope etching is used to prepare cross-sectional SEM samples. In slope etching, profiles of the sample are exposed using the ion beam, a region of the sample being protected, by a mask arranged on the surface of the sample or aligned with respect to the surface of the sample, from material removal by the ion beam. An ion beam slope etching process that has proven particularly effective for producing high-quality SEM samples is one in which at least two ion beams, preferably three ion beams, are guided onto the sample surface at a predefined angle to one another. This method is disclosed in WO 2008/106815 A2.
The ion beam etching units known from the existing art and currently on the market have the disadvantage that a manual sample switchover is necessary after each etching operation. In most cases, a sample switchover requires aeration and opening of the vacuum chamber, as well as re-application of the vacuum. In ion beam etching units that work with an airlock, inward and outward lock transfer is necessary at each sample switchover. These transfer operations also necessitate aeration and deaeration of portions of the unit. Sample switchovers of this kind are time-consuming, and result in low equipment capacity utilization, low sample throughput, and consequently poor cost-effectiveness. It is furthermore impossible to utilize the capacity of such apparatuses over a long period of time (e.g. overnight) without requiring a manual sample switchover by an operator. In addition, as a result of aeration, each sample switchover represents an opportunity for contamination with airborne particles, requiring that the equipment be serviced at shorter time intervals.
German Published Application 2313 096 describes a sample holder for etching thin layers, in which multiple samples are positioned selectably on a turntable into an ion beam.